The present invention generally relates to centrifugal separators and more particularly relates to centrifugal oil filters for engine and vehicle applications.
Current heavy-duty diesel engines put a moderate amount of soot (a form of unburned fuel) into the oil pan. This soot is generated due to the fuel hitting the cold cylinder walls and then being scraped down into the oil sump when the pistons reciprocate in the cylinders. Up until recently, the nitrous oxide emission regulations in the United States and other countries have been high enough that the fuel injection timing could be such that the level of soot generated was not high. In typical applications, the soot level would be under 1% (by weight) of the engine oil at oil drain time. At these low levels, soot in the oil does not cause any significant wear problems.
Recently, there has been a move to significantly lower nitrous oxide emissions which requires much retarded fuel injection timing, which significantly increases the amount of soot being generated. At reasonable oil drain intervals, the soot level may be as high as 4 or 5% with retarded injection timing. When the soot level gets this high, lubrication at critical wear points on the engine becomes so poor that high wear results, significantly decreasing the miles to overhaul and causing high operator expense.
Thus, the engine manufacturer has two choices, suffer very high warranty costs and low miles to overhaul, or significantly lower oil drain intervals to keep high soot levels out of the oil. Neither of these choices is desirable, so there is a current strong need to have a means of getting the soot out of the oil, the subject of this invention.
A problem with removing the soot from oil is that it is very small in sizexe2x80x94around 0.1 to 2.0 micrometers. To remove such small particles from oil using barrier filtration is not feasible due to the large filter size required and the very high probability that the filter will become plugged very rapidly due to trying to filter to such a fine level.
One way that is feasible to remove the soot from the oil is by using a centrifuge, a device that removes the soot from the oil using centrifugal force. This type of device is used to separate blood constituents from blood and has many other applications in typical laboratory applications. The use of a centrifuge for an engine brings a requirement of doing it in a very inexpensive and reliable manner with the centrifuge being easily changed at oil change time. Heretofore, centrifugal filters have not been able to sufficiently remove soot from oil, sufficiently retain the soot, nor reliable enough for use in engine and vehicle applications.
It is an objective of the present invention to provide a reliable and practical apparatus for removing soot from oil in engine applications.
The present invention is directed toward a novel centrifuge cartridge having several aspects beneficial for filtering soot from oil or contaminants from other fluid. The centrifuge cartridge is adapted to be rotated in a centrifuge housing about a predetermined axis for filtering fluid.
According to one aspect, the present invention is directed toward a centrifuge cartridge that prevents wave formation in the spinning oil contained within the cartridge during centrifugal filtering. According to this aspect, the cartridge includes a shell surrounding the predetermined axis defining an internal filter chamber. The filter chamber includes a plurality of radial partition walls for preventing wave formation in the fluid. Each partition wall extends radially inwardly from the shell toward the predetermined axis. The partition walls are radially spaced about the predetermined axis and divide the filter chamber into separate filter sections at different respective radial locations about the predetermined axis.
According to another aspect, the present invention is directed toward a novel centrifuge cartridge that has a long winding flow path which may maintain a long average residence time for substantially all oil in the cartridge and which may prevent short circuiting of oil. According to this aspect, the centrifuge cartridge includes a cup shaped shell including inner and outer walls surrounding a predetermined axis that are joined at the bottom. A filter chamber is defined between inner and outer shell walls. The filter chamber has an entrance for receiving unfiltered fluid and an exit for returning filtered fluid. To provide the long winding flow path, an intermediate annular wall surrounding the predetermined axis is arranged between the inner and outer walls to divide the filter chamber into first and second flow paths. The separate flow paths are adapted to communicate fluid in opposite axial directions. The flow paths are joined in proximity to an axial end of the centrifuge cartridge. One flow path is defined between the intermediate annular wall and inner wall. The other flow path is defined between the intermediate annular wall and the outer wall.
According to yet another aspect of the present invention, the present invention is directed toward a novel centrifuge cartridge in which unfiltered oil enters through top end and filtered oil exits through a bottom end, and which oil is retained in the cartridge when idle and not allowed to leak out. According to this aspect, the centrifuge cartridge includes a cup shaped shell having inner and outer walls extending axially and surrounding the predetermined axis. The inner and outer walls are joined at their bottom. A filter chamber is defined between inner and outer walls. The filter chamber has a fluid exit for outputting filtered fluid and an annular fluid entrance adapted to receive unfiltered fluid through a top end of the of the centrifuge cartridge. The inlet is coaxial about the predetermined axis at a location between the inner and outer walls. The exit is also proximate the top end of the cartridge but is connected to the bottom of the cartridge by an outlet conduit surface formed along the inside peripheral surface of the inner wall. The inner peripheral surface extending axially downward to provide for an outlet port exiting through a bottom end of the cartridge.
According to yet another aspect of the present invention, the present invention is directed toward a novel centrifuge cartridge in which oil enters through an exposed annular inlet of the cartridge through gravity from a stationary source offset from the axis of rotation. According to this aspect, the centrifuge cartridge comprises a cup shaped shell having inner and outer walls extending axially and surrounding the predetermined axis. The inner and outer walls of the shell are joined at their bottom. The cartridge also includes a lid secured to a top end of the shell. An annular inlet is provided vertically through the lid and coaxial about the predetermined axis for receiving unfiltered oil at a location offset from the predetermined axis. The annular inlet feeds unfiltered fluid to a filter chamber defined between inner and outer walls. The filter chamber has an exit located radially inward of the annular inlet and in proximity to a top end of the filter chamber such that substantially all fluid contained in the cartridge during rotation is retained in the filter chamber when the cartridge is idle.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.